JP2000340202A - Alkaline storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent short-circuit by enhancing strength of a separator on an outer side of a positive electrode plate of a group of coiled electrodes causing short-circuit without degrading battery characteristics. SOLUTION: A thickness and weight of a first separator 13 arranged on an outer side of a positive electrode plate 11 of a group of electrodes 10A are greater than a thickness and weight of a second separator 14 arranged on an inner side of the positive electrode plate 11. An occupying rate of the separators in a battery is approximately equal to a case that the thickness and weight of the first and second separators are equal. With this structure, short-circuit caused by a chip and a breakage of the positive electrode plate on the outer side of the positive electrode plate 11 is prevented without degrading battery characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkaline storage battery such as a nickel-cadmium storage battery and a nickel-hydride storage battery, and more particularly to an alkaline storage battery having an electrode group in which a positive electrode plate and a negative electrode plate are wound via a separator. The present invention relates to a configuration of an electrode group.

[0002]

2. Description of the Related Art Generally, nickel-cadmium storage batteries,
Alkaline storage batteries such as nickel-hydride storage batteries have a separator interposed between a positive electrode plate and a negative electrode plate, which are spirally wound to form an electrode group, and current collectors are connected to upper and lower ends of the electrode group. An electrode body is formed. This electrode body is housed in a cylindrical metal battery can, a current collecting lead plate extending from the current collector for the positive electrode is welded to the lower surface of the sealing body, and an electrolyte is injected. It is hermetically sealed by attaching a sealing body with a gasket interposed.

For example, in a nickel-cadmium storage battery, a nickel positive electrode plate in which a nickel sintered substrate is filled with a predetermined amount of a nickel active material by a chemical impregnation method, and a nickel cadmium storage device having a predetermined amount of cadmium by a chemical impregnation method. After a cadmium negative electrode plate filled with an active material is produced, a spiral electrode group is formed by winding the nickel positive electrode plate and the cadmium negative electrode plate with a separator interposed therebetween.

[0004]

By the way, in recent years, high capacity and high output of this kind of alkaline storage battery have been demanded.
In order to cope with this, the active material is packed at a high density, and the thickness of the separator is also reduced. However, as described above, in a battery using an electrode plate filled with an active material at a high density or a separator having a reduced thickness, there has been a problem that the incidence of short circuits increases.

[0005] Then, when the cause of the short circuit was investigated by disassembling the battery in which the short circuit occurred, cracks, burrs, chipping or breakage of the active material occurred in the positive electrode plate outside the positive electrode plate of the spiral electrode group. It was also found that fragments and powders based on these cracks, burrs, chipping or breakage of the active material penetrated the separator, and short circuits occurred frequently. On the other hand, inside the positive electrode plate of the spiral electrode group, almost no short circuit occurred due to cracks, burrs, chipping or breakage of the active material of the positive electrode plate.
This is because, in order to cope with higher capacity and higher output, the positive electrode plate filled with the active material with high density becomes brittle, and cracks, burrs, and active material on the positive electrode plate when spirally wound. It is thought that chipping and breakage occurred, and the separator was thinned, resulting in reduced strength.Fragments and powder generated by cracks, burrs, and chipping or breakage of the active material penetrated the separator outside the positive electrode plate. Can be

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been made in consideration of the above-described problems. It is an object of the present invention to reinforce the strength of the separator outside the positive electrode plate so that a short circuit does not occur. For this reason, in the alkaline storage battery of the present invention, the thickness of the first separator disposed outside the positive electrode plate of the spiral electrode group is larger than the thickness of the second separator disposed inside the positive electrode plate. .

As described above, by making the thickness of the first separator disposed outside the positive electrode plate of the electrode group larger than the thickness of the second separator disposed inside the positive electrode plate,
Since the mechanical strength of the first separator disposed outside the positive electrode plate can be reinforced, it is possible to prevent fragments and powder generated by cracks, burrs, chipping or breakage of the active material from penetrating through the separator. And the occurrence of a short circuit can be prevented. In this case, the first separator and the second separator
If the thickness of the separator is equal and the occupancy of the separator in the battery is substantially equal, the mechanical strength of the first separator can be reinforced without lowering battery characteristics such as discharge capacity and operating voltage, The occurrence of a short circuit can be prevented.

When the thickness of the first separator is made larger than the thickness of the second separator, the first separator can be formed by using two separators having a smaller thickness than the second separator. In this case, the thickness of the first separator can be made larger than the thickness of the second separator only by arranging and winding two thin separators on the outside of the positive electrode plate. Therefore, this kind of electrode group can be obtained easily and easily.

[0009] Even if the basis weight of the first separator disposed outside the positive electrode plate of the electrode group is larger than the basis weight of the second separator disposed inside, the first separator and the second separator are not separated. When the basis weight is equal to that of the separator in the battery and the occupancy of the separator is substantially equal, the mechanical properties of the first separator disposed outside the positive electrode plate can be reduced without lowering battery characteristics such as discharge capacity and operating voltage. Since the strength can be reinforced, fragments and powder generated by chipping or breakage of the positive electrode plate can be prevented from penetrating the separator,
The occurrence of a short circuit can be prevented.

Further, when the thickness and the basis weight of the first separator disposed outside the positive electrode plate of the electrode group are made larger than the thickness and the basis weight of the second separator disposed inside the positive electrode plate, the first and second separators are formed. If the separator occupancy rate in the battery is equal to the case where the thickness and the basis weight of the separator are equal, the mechanical strength of the first separator can be further increased without lowering the battery characteristics such as the discharge capacity and the operating voltage. Therefore, it is possible to further prevent fragments or powder generated by chipping or breakage of the positive electrode plate from penetrating the separator, and to sufficiently prevent occurrence of a short circuit.

Further, in the alkaline storage battery of the present invention, the first separator and the second separator are formed such that the split short fibers and the split long fibers made of polyolefin resin fibers are uniformly entangled, and the basis weight of the first separator is increased. It is larger than the basis weight of the second separator. As described above, when the short fibers and the long fibers are entangled with each other, the short fibers increase the surface area of the separator, improve the liquid retaining property of the electrolytic solution, and can suppress an increase in battery internal pressure. At the same time, the porosity of the separator is improved by the long fibers, and the gas permeability is improved. For this reason, it is possible to prevent the occurrence of an internal short circuit in an alkaline storage battery using such a separator, improve the active material utilization rate based on good liquid retention, and prevent an increase in the internal gas pressure.

[0012]

DETAILED DESCRIPTION OF THE INVENTION First Embodiment A first embodiment in which the present invention is applied to a nickel-cadmium storage battery will be described below with reference to the drawings. In addition,
FIG. 1 is a perspective view showing a main part of an electrode group of a first example of the first embodiment, FIG. 2 is a perspective view showing a main part of an electrode group of a second example of the first embodiment, FIG. 3 is a perspective view showing a main part of an electrode group of a comparative example of the first embodiment.

1. Preparation of Nickel Sintered Substrate First, a slurry is prepared by kneading a thickener such as carboxymethylcellulose and water into nickel powder, and this slurry is applied to conductive cores 11a and 12a made of nickel punched metal. Thereafter, the conductive cores 11a and 12a to which the slurry has been applied are sintered in a reducing atmosphere to produce a nickel sintered substrate having a porosity of 80%.

2. Preparation of Nickel Positive Electrode A predetermined amount of nickel active material is filled in the nickel sintered substrate prepared as described above by a chemical impregnation method. That is, the nickel sintered substrate is immersed in an aqueous solution mainly composed of nickel nitrate, and nickel nitrate is precipitated in the pores of the nickel sintered substrate. An active material conversion treatment for replacing the precipitated nickel nitrate with nickel hydroxide is performed. The same processing step is repeated a predetermined number of times (for example, 6 to 8 times) to produce a nickel positive electrode plate 11 in which a nickel sintered substrate is filled with a predetermined amount of a nickel active material mainly composed of nickel hydroxide.

3. Preparation of Cadmium Anode Plate A predetermined amount of a cadmium active material is filled into the nickel sintered substrate prepared as described above by a chemical impregnation method. That is, a nickel sintered substrate is immersed in an aqueous solution mainly composed of cadmium nitrate to precipitate cadmium nitrate in pores of the nickel sintered substrate, and then immersed in an alkaline aqueous solution (for example, sodium hydroxide aqueous solution). Then, an active material conversion treatment for replacing cadmium nitrate precipitated in the pores with cadmium hydroxide is performed. The same process is repeated a predetermined number of times (for example, 6 to 8 times) to produce a cadmium negative electrode plate 12 in which a nickel sintered substrate is filled with a predetermined amount of a cadmium active material mainly composed of cadmium hydroxide.

4. Production of Electrode Group (1) Example 1 First, a nonwoven fabric made of polyethylene or polypropylene was 0.20 mm thick and had a basis weight of 85 g / m2.
^{A second} separator 13 is prepared and is made of a nonwoven fabric made of polyethylene or polypropylene.
A second separator 14 having a thickness of 0.16 mm and a basis weight of 65 g / m ² is prepared. Then, as shown in FIG.
These first separator 13 and second separator 14
And the nickel positive electrode plate 11
The cadmium negative electrode plate 12 was laminated so as to be arranged outside the separator 13 of Example 1 and spirally wound to produce a spiral electrode group 10A of Example 1.

(2) Example 2 First, a nonwoven fabric made of polyethylene or polypropylene, having a thickness of 0.10 mm and a basis weight of 45 g / m2
^{In addition to} preparing two first separators 15, the second separator 15 is made of polyethylene or polypropylene non-woven fabric and has a thickness of 0.16 mm and a basis weight of 65 g / m ² .
(The same as the second separator 14 of the first embodiment) is prepared. Then, as shown in FIG. 2, the first separators 15, 15 are overlapped, and the nickel positive electrode plate 11 is arranged between the first separators 15, 15 and the second separator 14 thus overlapped. At the same time, the cadmium negative electrode plates 12 were stacked outside the first separators 15, 15 and spirally wound to produce a spirally wound electrode group 10 </ b> B of Example 2.

(3) Comparative Example First, a nonwoven fabric made of polyethylene or polypropylene was 0.18 mm thick and had a basis weight of 75 g / m2.
² , two separators 16, 16 are prepared. Then
As shown in FIG. 3, the nickel positive electrode plate 11 is arranged between the separators 16, 16, and the cadmium negative electrode plate 12 is laminated outside the separator 16, and spirally wound. Spiral electrode group 1 of comparative example
0C was produced.

5. Production of Nickel-Cadmium Storage Battery Next, a positive electrode current collector is welded to the end of the conductive core 11a exposed at the upper end of these electrode groups 10A, 10B, 10C, and the conductive core 12a exposed at the lower end. After the negative electrode current collectors were welded to the end portions, these were inserted into a bottomed cylindrical battery can in which nickel was plated on iron. Then
The negative electrode current collector was welded to the inner bottom surface of the battery can, and the tip end of the current collecting lead plate extending from the positive electrode current collector was welded to the bottom surface of the sealing body. % Aqueous potassium hydroxide).

Thereafter, the sealing body is placed in the opening of the battery can via an insulating gasket, and the end of the opening of the battery can is crimped inward to hermetically close the battery so that the nominal capacity is 1.
Each nickel-cadmium storage battery A, B, C of 7 Ah SC size was produced. The nickel-cadmium storage battery using the electrode group 10A is referred to as the battery A of Example 1, the nickel-cadmium storage battery using the electrode group 10B is referred to as the battery B of Example 2, and the nickel-cadmium storage battery using the electrode group 10C. Was designated as Battery C of Comparative Example.

6. Test (1) Short-circuit measurement Each of the batteries A, B, and C produced as described above was prepared by 10,000 each, and the open-circuit voltage of each of the 10,000 batteries A, B, and C was measured. When a voltage of 4 V or less was determined to be a short circuit, and a short circuit occurrence rate was obtained, the results shown in Table 1 below were obtained.

[0022]

[Table 1]

As is clear from Table 1, the short-circuit occurrence rate of the battery A of Example 1 and the battery B of Example 2 are reduced. This is the electrode group 10A (10B)
The thickness and the basis weight of the first separator 13 (15, 15) arranged outside the nickel positive plate 11
This is because the strength was reinforced because the separator 14 was larger than the thickness and the basis weight.

(2) High Rate Discharge Characteristics and Internal Gas Pressure Next, each of the batteries A, B, and C produced as described above was subjected to a charge current of 1.7 A (1 C) in a 25 ° C. temperature atmosphere. After charging for 72 minutes and suspending charging for 60 minutes, the battery was discharged at a constant current (2 A, 10 A, 30 A). When the battery voltage reached 0.8 V, the discharge was stopped. When the operating voltage was determined, the results were as shown in Table 2 below.

[0025]

[Table 2]

On the other hand, each of the batteries A, B, and C produced as described above was subjected to 2 A at a temperature of 25 ° C.
The battery is charged with a (constant current) charging current, and the peak value of the battery voltage at the end of charging is stored. When the voltage drops by a certain value with reference to this, charging is terminated.
The battery was discharged at a (constant current) discharge current until the battery voltage reached 0.7 V, and the battery was discharged for 1 hour. A −Δ cycle test was performed, and the internal pressure (maximum gas pressure) of each battery during 2A discharge was measured. Table 3 shows the results. Similarly, a −Δ cycle test was performed at a discharge current of 10 A (constant current), and the internal pressure (maximum gas pressure) of each battery during 10 A discharge was measured. The results shown in Table 3 below were obtained. .

[0027]

[Table 3]

As is clear from the results shown in Tables 2 and 3, even the battery A of Example 1 is different from the battery B of Example 2.
However, the high-rate discharge capacity, operating voltage, and internal gas pressure were almost the same as those of the battery C of the comparative example, and a decrease in high-rate discharge characteristics, a decrease in operating voltage, and an increase in internal gas pressure were observed. Did not.

This corresponds to the electrode group 10A of the battery A of the first embodiment.
In the first embodiment, the second
1. Separator 13 thickness (0.20 mm) and basis weight
(85 g / m^Two) Is the thickness of the inner second separator 14
(0.16 mm) and the basis weight (65 g / m^Two) Bigger
In any case, the thickness and the basis weight of the second separator 14 are compared.
The thickness (0.18 mm) of the separators 16 and 16 of the comparative example
And basis weight (75 g / m ^Two), That is, the average
Thickness (0.18 mm) and average basis weight (75 g / m2)
^Two) Is equal to the separators 16 and 16 of the comparative example.
This is because the occupation ratios within are equal.

Further, in the electrode group 10B of the battery B of the second embodiment, the first
Thickness of the separators 15, 15 (0.20 in total of the two sheets)
mm) and basis weight (also greater than the second thickness of the separator 14 90 g / m ²⁾ by two total inner (0.16 mm) and basis weight (65 g / m ^2), the second separator 14 The thickness and the basis weight of the separator 16 of the comparative example,
16 thickness (0.18 mm) and basis weight (75 g /
m ² ), that is, the average thickness (0.18 m
m) is equal to the separators 16 and 16 of the comparative example, and the average basis weight (77.55 g / m ² ) is set to the separator 1 of the comparative example.
This is because the occupation ratio in the battery is made substantially equal to that of the batteries 6 and 16.

As described above, in the alkaline storage battery of the present invention, the thickness and basis weight of the first separators 13 (15, 15) located outside the positive electrode plate 11 of the spiral electrode group are increased, and Since the thickness and the basis weight of the second separator 14 located inside the battery are reduced to equalize the occupancy of the separator in the battery, the cathode plate outside the cathode plate 11 without deteriorating the battery characteristics Cracks, burrs, and short-circuiting due to chipping or breakage of the active material can be prevented.

In the first embodiment described above,
An example in which the first separator and the second separator are used separately has been described. However, the first and second separators are formed as one separator, and the thickness and the thickness are set so that one half of the first and second separators becomes the first separator. The weight of which is adjusted and the thickness and the weight of which are adjusted so that the other becomes the second separator can be used. In the nickel-cadmium storage battery of the first embodiment described above, both the positive electrode plate and the negative electrode plate used sintered electrode plates, but experiments were conducted using batteries using non-sintered electrode plates such as a paste type. Similar results were obtained in these cases.

B. Second Embodiment Next, a second embodiment in which the present invention is applied to a nickel-hydride battery will be described with reference to FIG. In addition,
FIG. 4 is a perspective view showing a main part of the electrode group according to the second embodiment.

1. Preparation of Nickel Positive Electrode A positive electrode active material slurry was prepared by mixing 100 parts by weight of a positive electrode active material powder mainly composed of nickel hydroxide and 50 parts by weight of an aqueous solution in which 0.2% by weight of hydroxypropyl cellulose was dissolved. . This positive electrode active material slurry is filled into 95% porosity nickel foam 21a, dried,
This was rolled to produce a nickel positive electrode 21. In addition, the positive electrode active material slurry was prepared by foaming nickel 21a having a porosity of 95%.
Was charged so that the nominal capacity of the battery became 1200 mAh.

2. Preparation of hydrogen storage alloy negative electrode A hydrogen storage alloy paste was prepared by adding a binder such as potetafluoroethylene (PTFE) and an appropriate amount of water to a hydrogen storage alloy powder prepared using a high-frequency melting furnace and mixing them. . Next, this hydrogen storage alloy paste was applied to both surfaces of a negative electrode substrate 22a made of punched metal, dried, and then pressed to a predetermined thickness to produce a hydrogen storage alloy negative electrode 22. When the hydrogen storage alloy paste is applied to the negative electrode substrate 22a, the nominal capacity of the battery is 200
The amount of the hydrogen storage alloy paste was applied so as to be 0 mAh.

3. Production of Separator (1) Production of First Base Cloth (Dry Base Cloth) Long fibers composed of split fibers (split fibers) having a fiber length of 25 mm or more (for example, 50 mm) mainly composed of a polyolefin resin are scattered in the air. And collected with a wire mesh to obtain a fiber density (basis weight) of 20 g / m ² and 30 g / m ^2.
The first base fabric was prepared by dry paper making so as to obtain m ² .

(2) Preparation of second base fabric (wet base fabric) Short fibers composed of split fibers (split fibers) mainly composed of polyolefin resin and having a fiber length of 10 mm or less (for example, 6 mm) are dispersed in water. The fiber density (basis weight) is 20 g / m ² , 25 g / m ² , 30 g / m ² , 35
The second base fabric was produced by wet paper making so as to obtain g / m ² , 40 g / m ² , 45 g / m ² , and 50 g / m ² .

(3) Preparation of Composite Base Fabric Next, a first base fabric having a fiber density (basis weight) of 20 g / m ² prepared as described above, and a fiber density (basis weight) of 20 g / m ² were prepared.
/ M ² , 25 g / m ² , 30 g / m ² , 35 g / m ² , 40
g / m ² , 45 g / m ² , and 50 g / m ² second base cloths were laminated and laminated to form a two-layer laminate, and a high-pressure water stream was discharged through the two-layer laminate. The fibers are subjected to a hydroentanglement treatment to form a composite such that the short fibers and the long fibers are uniformly entangled, and the fiber density (basis weight) is 40 g / m ² , 45.
g / m ² , 50 g / m ² , 55 g / m ² , 60 g / m ² , 6
Composite base fabrics of 5 g / m ² and 70 g / m ² were prepared, respectively.

Further, the first base cloth of fiber density produced as described above (basis weight) of 30 g / m ^2, the fiber density (basis weight) of a second base fabric of 30 g / m ² so as to overlap each After laminating to form a two-layer laminate, the two-layer laminate is subjected to a hydroentanglement process of discharging high-pressure water flow,
The short fibers and the long fibers were compounded so as to be uniformly entangled to prepare a composite base fabric having a fiber density (basis weight) of 60 g / m ² .
Each of these composite base fabrics was a1 (40 g / m ² ), b1 (45 g / m ² ), c1 (50 g / m ^2).
), D1 (55 g / m ² ), e1 (60 g
/ M ² ), f1 (65 g / m ² ), g1 (7
Things 0 g / m ^2), and a h1 (since the base fabric 30 g / m ² second base fabric those with 30 g / m ² of 60 g / m ^2).

After the first base cloth made of short fibers and the second base cloth made of long fibers are laminated and laminated, the short fibers and long fibers are entangled with each other by hydroentanglement. The short fibers and the long fibers are uniformly and satisfactorily entangled. As a result, the surface area of the separator is increased by the short fibers, the liquid retention of the electrolyte is improved, and the increase in the internal pressure of the battery can be suppressed. In addition, the porosity of the separator is improved by the long fibers, and the gas permeability is improved. improves.

(4) Hydrophilizing treatment Thereafter, each of the composite base fabrics a1, b1, and c whose thickness has been adjusted
1, d1, e1, f1, g1, and h1 are respectively put into a reaction vessel, and the inside of this vessel is evacuated, and then a reaction gas obtained by diluting fluorine gas with nitrogen gas is introduced into the reaction vessel. Was reacted with a reaction gas for 1 minute to perform a hydrophilic treatment, thereby producing each separator. When the respective fibers are subjected to a hydrophilization treatment, the respective fibers are hydrophilized and the hydrophilicity is improved. The hydrophilization treatment may be a corona discharge treatment, a sulfonation treatment, a surfactant treatment, or the like, in addition to the above-described fluorine gas treatment.

The separator using the composite base cloth a1 is used as the separator a, the separator using the composite base cloth b1 is used as the separator b, the separator using the composite base cloth c1 is used as the separator c, and the composite base cloth d1 is used. The separator using the composite base fabric e1 is referred to as a separator e, the separator using the composite base fabric f1 is referred to as a separator f, the separator using the composite base fabric g1 is referred to as a separator g, and the composite base fabric h1 is referred to as a separator g. Was used as a separator h. Table 4 below summarizes the configuration of the separator described above. Since each separator is subjected to a hydrophilic treatment, the use of the separator improves the liquid retention of the electrolytic solution, improves the active material utilization rate, and improves the discharge capacity of the alkaline storage battery. Become.

[0043]

[Table 4]

4. Production of Nickel Metal Hydride Battery Next, any one of these separators a to h is used as a first separator 23, and any one of these separators a to h is used as a second separator 24. The nickel positive electrode plate 21 manufactured as described above is arranged between the separator 24 and the hydrogen storage alloy anode 22 manufactured as described above is stacked outside the first separator 23. Then, the spirally wound electrode group 20 was formed by spirally winding.

Next, a positive electrode current collector is welded to the end of the conductive core 21a exposed at the upper end of the electrode group 20,
After welding the negative electrode current collector to the end of the conductive core 22a exposed at the lower end, these were inserted into a bottomed cylindrical battery can in which nickel was plated on iron. Next, the negative electrode current collector is welded to the inner bottom surface of the battery can, and the tip of the current collecting lead plate extending from the positive electrode current collector is welded to the bottom surface of the sealing body, so that a predetermined amount of the electrolytic solution is contained in the battery can. (30% by weight aqueous solution of potassium hydroxide) was injected.

Thereafter, the sealing body is placed on the opening of the battery can through an insulating gasket, and the end of the opening of the battery can is crimped inward to hermetically close the battery so that the nominal capacity is 1.
2Ah AA size nickel-hydride storage batteries D ~
K was produced. Here, a battery D (X + Y = 110, X / Y = 1...) Using the separator e as the first separator and the separator c as the second separator.
2). Similarly, a battery E (X + Y = 110, X / Y = 1.4) using the separator f and the separator b is used.
The battery F (X + Y = 110, X / Y = 1.75) was obtained using the separator g and the separator a.

Similarly, the battery G (X + Y = 110, X / Y = 0.8) using the separator c and the separator e was used.
3), a battery using the separator d and the separator d is referred to as a battery H (X + Y = 110, X / Y = 1), and a battery using the separator f and the separator e is referred to as a battery I (X + Y = 1).
25, X / Y = 1.08), and the battery using the separator c and the separator c was used as a battery J (X + Y = 100, X / Y).
= 1), and a battery using the separator h and the separator c was designated as a battery K (X + Y = 110, X / Y = 1.2).
In addition, X (g / m ² ) in the parentheses indicates the weight of the first separator 23, and Y (g / m ² ) indicates the weight of the second separator 24.

5. Measurement (1) Measurement of winding diameter of spiral electrode body Used for each of the batteries D to K manufactured as described above.
The diameter of the spiral electrode group is measured, and the first
Both the basis weight of the second separator 24 is 55 g / m. ^TwoBattery
Assuming that the diameter of the spiral electrode group used for H is 100,
Is calculated as a winding diameter ratio (%), as shown in Table 5 below.
Results.

(2) Initial Activation of Batteries Each of these batteries DK was charged with a charging current of 120 mA (0.1
C) for 16 hours, pause for 1 hour and discharge current 2
After discharging at 40 mA (0.2 C) until the discharge end voltage reaches 1.0 V, the apparatus is paused for 1 hour. This charge / discharge was repeated three times to activate each of the batteries DK.

(3) Measurement of Short-Circuit Occurrence Rate The open-circuit voltage of each of the batteries D to M before activation prepared as described above was measured. Was obtained, the results shown in Table 5 below were obtained.

(4) Measurement of Battery Internal Pressure Each of the batteries D to M activated as described above is charged at a charging current of 1200 mA (1 C). When measured, the results were as shown in Table 5 below.

[0052]

[Table 5]

As is clear from Table 5, the batteries D (X = 60, Y = 50) and E (X = 65, Y = 50) in which the basis weight of the first separator is larger than the basis weight of the second separator.
45), battery F (X = 70, Y = 40), battery I (X =
65, Y = 60) and a battery G (X = 50, Y = 50) in which the short-circuit occurrence rate of the battery K (X = 60, Y = 50) is low and the basis weight of the first separator is smaller than the basis weight of the second separator. 6
0), battery H (X = 55, Y = 55), battery J (X = 5
(0, Y = 50). In addition, when the battery H was disassembled and the short-circuited portion was examined, all of the short-circuits occurred outside the positive electrode plate 21. For this reason, the first separator 2 disposed outside the positive electrode plate 21
It can be said that if the basis weight of No. 3 is larger than the basis weight of the second separator disposed inside the positive electrode plate 21, the short-circuit occurrence rate decreases.

The battery D (X = 60, Y = 50) and the battery K (X = 60, Y = 50) are compared.
It can be understood that the short circuit rate is lower than that of the battery K. This is because even if the basis weight of the first separator 23 is the same, the basis weight of the second base fabric constituting the first separator 23 is different (40 g / m ² for the battery D and 30 g for the battery K).
/ M ² ). This is because, when the basis weight of the second base fabric is increased, the ratio of the short fibers having a fiber length of 10 mm or less is larger than that of the long fibers having a fiber length of 25 mm or more, so that the long fibers and the short fibers are uniformly entangled. It is considered that the variation of the basis weight was suppressed, and the short-circuit occurrence rate was reduced. From this, it can be said that it is preferable to increase the basis weight of the second base fabric constituting the first separator 23 even if the basis weight of the first separator 23 is the same.

Battery F has a low short-circuit occurrence rate, but has a large increase in battery internal pressure. This means that the basis weight of the first separator is 70 g / m ² and the basis weight of the second separator is 40 g / m ^2.
greatly different from g / m ^2, unlike the distribution of the electrolyte to the basis weight difference is large, it can be considered that the battery internal pressure rises caused variations in gas absorption reaction of the hydrogen storage alloy negative electrode 22. From this, even if the basis weight of the first separator is larger than the basis weight of the second separator, it is necessary to make the basis weight of the second separator smaller than 1.75 times, preferably 1.5 times or less. It is preferred that

Battery I has a low short-circuit occurrence rate, but has a winding diameter ratio of 1
05 (the sum of the basis weights of the first separator and the second separator is 125 g / m ² ), which causes a problem that it is difficult to insert the battery into the battery can. In addition, since the occupancy of the separator in the battery can is increased, the remaining porosity in the battery is reduced, so that gas absorption becomes difficult,
It is considered that the battery internal pressure increased. From this, the first
Even if the basis weight of the separator is larger than the basis weight of the second separator, it is necessary to reduce the basis weight of the second separator by an amount corresponding to the basis weight of the first separator, and to make the sum of these basis weights equal. be able to.

(5) Measurement of cycle life Next, each of the batteries D to M activated as described above was
After charging at a charging current of 1200 mA (1 C) for 16 hours,
A charge / discharge cycle in which the battery is stopped for 1 hour and discharge is performed at a discharge current of 1200 mA (1 C) until the discharge end voltage reaches 1.0 V is repeated, and a discharge capacity is obtained from a discharge time in each cycle, and a ratio to the initial capacity. Was obtained as the battery capacity ratio, and the result as shown in FIG. 5 was obtained.

As is apparent from FIG. 5, the cycle life of the batteries D, E, G, H, and K is long, and the cycle life of the batteries J, I, and F is short. Here, since the sum of the weights of the first and second separators is 100, the weight of the battery J is smaller than those of the other separators and the winding diameter is smaller, the holding amount of the electrolyte is small, and It is considered that the amount of liquid retained decreased and the cycle life was shortened. Further, as described above, the battery I has a high winding diameter ratio, increases the occupancy of the separator in the battery can, reduces the remaining space ratio in the battery, makes it difficult to absorb gas, and increases the internal pressure of the battery. It is considered that the cycle life was shortened and the cycle life was shortened. Further, battery F
As described above, since the basis weight of the separator is largely different between the inside and outside of the positive electrode plate, it is considered that the gas absorption reaction varies, the internal pressure of the battery increases, and the cycle life is shortened.

On the other hand, the batteries G and H have a long cycle life, but since the basis weight of the first separator is smaller than the basis weight of the second separator, short-circuiting occurs outside the positive electrode plate due to insufficient strength of the first separator. Occurred, and the short-circuit occurrence rate increased. In consideration of these results, as in the batteries D and E, the basis weight of the first separator disposed outside the positive electrode plate is set to be larger than the basis weight of the second separator disposed inside the positive electrode plate, and Even if the basis weight of the second base fabric constituting the first separator 23 is increased and the basis weight of the first separator is larger than the basis weight of the second separator, the basis weight of the second separator is 1.5 times. By making it twice or less, a nickel-hydride storage battery having a low short-circuit occurrence rate, a small increase in battery internal pressure, and a long cycle life can be obtained.

As described above, in the second embodiment of the present invention, the first separator disposed outside the positive electrode plate and the second separator disposed inside the positive electrode plate are made of short fibers and long fibers. Are entangled with each other,
Variations in the basis weight of each separator can be prevented. When the separator thus formed is used, the basis weight of the first separator is larger than the basis weight of the second separator, so that the mechanical strength of the second separator is reinforced, and thus, Prevents internal short circuit of alkaline storage battery using separator

In the second embodiment described above,
The example in which the split base fiber is used as the long fiber in the first base cloth and the split short fiber is used as the short fiber in the second base cloth has been described. However, the split base fiber containing the long fiber composed of the split fiber is used in the first base cloth. A long fiber other than the above, for example, a long fiber made of an adhesive fiber may be blended. Similarly, short fibers other than split fibers are added to the second base cloth containing short fibers made of split fibers, for example,
Short fibers composed of adhesive fibers may be blended.

Further, in the second embodiment described above, an example was described in which short fibers having a fiber length of 6 mm were used as the short fibers, but the fiber length is not limited to 6 mm and may be 10 mm.
mm or less, and it is particularly preferable to use short fibers in the range of 3 to 10 mm from the viewpoint of manufacturing a separator. Further, in the above-described second embodiment, an example in which a long fiber having a fiber length of 50 mm is used as the long fiber has been described. It is preferable to use a long fiber in the range of 70 mm from the viewpoint of manufacturing a separator. Furthermore, in each of the above-described embodiments, an example in which the present invention is applied to a cylindrical storage battery has been described. However, the present invention is not limited to this, and it goes without saying that the present invention can be applied to various shapes of storage batteries such as a prismatic shape. .

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a main part of an electrode group according to Example 1 of a first embodiment of the present invention.

FIG. 2 is a perspective view showing a main part of an electrode group according to Example 2 of the first embodiment of the present invention.

FIG. 3 is a perspective view showing a main part of an electrode group of a comparative example of the first embodiment of the present invention.

FIG. 4 is a perspective view showing a main part of an electrode group according to a second embodiment of the present invention.

FIG. 5 is a diagram showing cycle life characteristics of each battery according to the second embodiment of the present invention.

[Explanation of symbols]

10A, 10B, 10C: electrode group, 11: nickel positive plate, 11a: conductive core, 12: cadmium negative plate, 1
2a: conductive core, 13: first separator, 14: second separator, 15, 15: first separator, 1
6, 16: separator, 21: nickel positive plate, 21a
... conductive core, 22 ... hydrogen storage alloy negative electrode plate, 22a ... conductive core, 23 ... first separator, 24 ... second separator,

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Etsuya Fujisaka 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Taimeo Hamamatsu 2 Keihanhondori, Moriguchi-shi, Osaka 5-5-5 Sanyo Electric Co., Ltd. (72) Inventor Satoru Yoneya 2-5-5 Sanyo Electric Co., Ltd. (72) Inventor Yasushi Maeda Yasushi Maeda Keihanmoto, Moriguchi, Osaka 2-5-5, Sanyo Electric Co., Ltd. (72) Inventor Masao Takee 2-5-5, Keihanhondori, Moriguchi-shi, Osaka F-term in Sanyo Electric Co., Ltd. 5H021 CC17 EE04 EE23 HH00 HH01 HH03 5H028 AA05 BB07 CC12 EE01 EE05 HH05

Claims (9)

[Claims] 1. An alkaline storage battery including an electrode group in which a positive electrode plate and a negative electrode plate are wound with a separator interposed therebetween, wherein a first separator is disposed outside a positive electrode plate of the electrode group, An alkaline storage battery, wherein a second separator is disposed inside the group of positive plates, wherein the thickness of the first separator is greater than the thickness of the second separator. 2. The method according to claim 1, wherein the first separator comprises two separators having a thickness smaller than that of the second separator, and the thickness of the first separator is made larger than the thickness of the second separator. The alkaline storage battery according to claim 1, wherein 3. An alkaline storage battery comprising an electrode group in which a positive electrode plate and a negative electrode plate are wound with a separator interposed therebetween, wherein a first separator is arranged outside a positive electrode plate of the electrode group, An alkaline storage battery, wherein a second separator is disposed inside the group of positive plates, and a basis weight of the first separator is larger than a basis weight of the second separator. 4. An alkaline storage battery including an electrode group in which a positive electrode plate and a negative electrode plate are wound with a separator interposed therebetween, wherein a first separator is disposed outside a positive electrode plate of the electrode group, An alkaline storage battery, wherein a second separator is disposed inside the group of positive plates, wherein the thickness and the basis weight of the first separator are larger than the thickness and the basis weight of the second separator. 5. An alkaline storage battery including an electrode group in which a positive electrode plate and a negative electrode plate are wound with a separator interposed therebetween, wherein a first separator is disposed outside a positive electrode plate of the electrode group, A second separator is disposed inside the group of positive plates, wherein the first separator and the second separator are:
An alkaline storage battery, wherein split short fibers and split long fibers made of a polyolefin-based resin fiber are uniformly entangled, and the basis weight of the first separator is larger than the basis weight of the second separator. 6. The weight of the first separator is set to the second
And the basis weight of the second separator is reduced by the extent that the basis weight of the first separator is increased, so that the occupancy of the separators present in the battery is equalized. Claim 5
3. The alkaline storage battery according to claim 1. 7. The first separator and the second separator are a base cloth mainly composed of split short fibers having a fiber length of 10 mm or less, and a base cloth mainly composed of divided long fibers having a fiber length of 25 mm or more. 7. The alkaline storage battery according to claim 5, wherein the fibers are uniformly compounded and the fibers are uniformly entangled. 8. The basis weight of a base fabric mainly composed of split short fibers having a fiber length of 10 mm or less used for the first separator is a divided short fiber having a fiber length of 10 mm or less used for the second separator. The basis weight is made larger than the basis weight of the base cloth mainly, and the basis weight of the base cloth mainly composed of the split filament fibers having a length of 25 mm or more is reduced by an amount corresponding to the increase in the basis weight of the base cloth. An alkaline storage battery according to claim 7. 9. The weight of the first separator is changed to the second separator.
9. The method according to claim 5, wherein the basis weight of the first separator is larger than the basis weight of the second separator, and the basis weight of the first separator is 1.5 times or less of the basis weight of the second separator. Alkaline storage batteries.